Method and apparatus for cleaning contaminated gases

ABSTRACT

A segmentally directed rotary spray generator for creating a high-velocity intense liquid spray having a definite arcuate shape with a relatively substantial effective depth useful with air pollution control equipment. The rotary spray generator having a plurality of blades symmetrically arranged radially on a rotatable ring support structure and a liquid supply pipe fitting within the ring structure having an angular orifice opening approximately equal to the angular segment of the spray to be generated.

United States Patent [72] Inventors Orlan M. Arnold Grosse Point Park;Victor W. Hanson, Garden City; Robert M. Jamison; Nicholas J. Panzica,both of Detroit; Emil Umbricht, Northville, all of Mich.

[21] Appl. No. 844,695

[22] Filed May 14, 1969 [45] Patented Dec. 7, 1971 [73] Assignee AjemLaboratories, Inc.

Livonia, Mich. Original application Apr. 8, 1968, Ser. No. 719,767, nowPatent No. 3,475,881, dated Nov. 4, 1969, which is a continuation ofapplication Ser. No. 586,812, Nov. 14, 1966, now abandoned. Divided andthis application May 14, 1969, Ser. No. 844,695

[54] METHOD AND APPARATUS FOR CLEANING CONTAMINATED GASES 8 Claims, 6Drawing Figs.

[52] U.S.Cl ..239/222.1l, 239/224, 239/505, 239/521 [51] Int. Cl B05b3/02,

[50] Field oESearch 239/505, 223,224,681,688,687,380,214,22211,521523,524,222,231,222.17,222.21

Primary Examiner- Lloyd L. King Attorney-Curtis, Morris & SaffordABSTRACT: A segmentally directed rotary spray generator for creating ahigh-velocity intense liquid spray having a definite arcuate shape witha relatively substantial effective depth useful with air pollutioncontrol equipment. The rotary spray generator having a plurality ofblades symmetrically arranged radially on a rotatable ring supportstructure and a liquid supply pipe fitting within the ring structurehaving an angular orifice opening approximately equal to the angularsegment of the spray to be generated.

METHOD AND APPARATUS FOR CLEANING CONTAMINATED GASES This is a divisionof copending application Ser. No. 7 19,767, filed Apr. 8, 1968, andissued on Nov. 4, 1969, as US. Pat. No. 3,475,881; which in turn was acontinuation of then copending application Ser. No. 586,812, filed Nov.l4, 1966, now abandoned.

The present invention relates, in general, to the removal ofcontaminants from contaminated gases and, in particular. to a method andapparatus for removing pollutants from the gaseous discharge of a cupolafurnace.

Public attention is being drawn more and more to the problem ofatmospheric pollution. The dangers and hazards to human, animal, andplant life presented by air pollution are increasing, particularly inurban, industrialized areas where the concentrations of population andmanufacturing activities already are great and are growing steadily. Airpollution also has caused damage and loss of property such as homes andautomobiles.

Civic organizations and governmental authorities at all levels aretaking more of an interest in the problem of atmospheric pollution andare seeking ways of preventing, controlling and minimizing air pollutionand its effects. Such action is manifested, for example, in the form ofstatutes, ordinances, codes, regulations, studies, and grants.Generally, these efforts are designed to strike at the heart of thepollution problem, namely, the major sources of air pollution wherecontaminants and pollutants are released to the atmosphere.

Illustrative of these sources of air pollution are steeland othermetal-refining operations, chemical manufacturing and processingfacilities, petroleum refineries, foundries and largescale paintingoperations. These facilities, as well as others, pollute the atmosphereas gases are exhausted from the particular operation. These gasescommonly contain foreign materials in the form of solid particulates oraerosols or mists.

Some strides have been made toward purifying gases produced inindustrial operations prior to their release into the atmosphere inorder to prevent air pollution. Often, these steps have been taken underthe pressure of governmental enforcement. In many cases, the equipmentemployed in purifying industrial gases has not performed adequately incomparison to regulations and codes, particularly where the regulationsand codes are stringent. This problem is becoming more acute in that thelocal governments in most industrial areas continue to enact stricterregulations and codes.

One of the more difficult problems in purifying industrial gases is theremoval of contaminants and pollutants which are of small size.Generally, ultrafine particles in the submicron size range constitute asignificant portion of the pollutants being discharged from anindustrial facility into the atmosphere. With the increasingly stringentrequirements on the level of contaminants, particularly in the submicronsize range, allowable to be vented to the atmosphere, the need hasarisen for the development of more efficient and effective pieces ofequipment for purifying industrial gases.

Accordingly, it is an object of the present invention to provide a newand improved method and apparatus for removing the contaminants from acontaminated gas.

It is another object of the present invention to provide new andimproved apparatus for removing the contaminants from a contaminated gaswhich operates in a highly efficient manner and is effective in removinga relatively high percentage of the contaminants.

It is yet another object of the present invention to provide contaminantremoval apparatus which is capable of handling relatively largequantities of contaminated gases.

it is still a further object of the present invention to providecontaminant removal apparatus which is versatile and reliable inoperation and easily assembled, serviced and maintained.

It is a specific object of the present invention to provide a new andimproved method and apparatus for removing the pollutants from thegaseous discharge of a cupola furnace.

Briefly, the method and apparatus of the present invention involvespreconditioning a contaminated gas to remove a portion of thecontaminants and to facilitate removal of the remaining contaminants ata subsequent stage by conventional gas washing techniques. Thispreconditioning includes saturating the contaminated gas with a waterspray and condensing the resulting vapor. The effect of this saturationand condensation is a cooling of the gas, a collection of a certainportion of the contaminants, generally the larger size contaminants, andthe formation of larger masses, generally containing the smaller sizecontaminants. By presenting the smaller size contaminants in largermasses to a conventional gas w'asher, the gas washer is more effectivein removing the smaller size contaminants.

In a specific embodiment of the present invention, the pollutant ladengaseous discharge of a cupola furnace, a major source of air pollution,is saturated and condensed in a downcomer positioned alongside thecupola furnace. The saturation is efiected by means of an intense waterspray through which the gaseous discharge is passed. Condensation iseffected either by means of cooling of the gaseous discharge below thesaturation temperature or the introduction of ambient air into thedowncomer or a combination of the two.

In the specification and in the accompanying drawings there aredescribed and shown an illustrative embodiment of the invention andvarious modifications thereof are suggested, but it is to be understoodthat these are not intended to be exhaustive, but on the contrary aregiven for purposes of illustration in order that others skilled in theart may fully understand the invention so that they may modify and adaptit in various forms, each as may be best suited to the conditions of aparticular use.

The various objects, aspects, and advantages of the present inventionwill be more fully understood from consideration of the followingspecification in conjunction with the accompanying drawings in which:

FIG. 1 illustrates apparatus constructed in accordance with the presentinvention for removing pollutants from the gaseous discharge of a cupolafurnace;

FIG. 2 is an enlarged showing of a portion of the downcomer of FIG. 1;

FIG. 3 is a horizontal section taken along line 3-3 of FIG. 2

FIG. 4 is a vertical section taken along line 4-4 of FIG. 3;

FIG. 5 is a horizontal section taken along line $--5 of FIG. 4; and

FIG. 6 is a horizontal section taken along line 6-6 of FIG. 2.

FIG. 1 illustrates pollutant removal apparatus constructed in accordancewith the present invention located alongside a cupola furnace 10. Thepollutant laden gaseous discharge of the cupola furnace 10 is suppliedto a downcomer 12 through a crossover 114. This gaseous discharge mayrangefin temperature from ambient temperature to 2,000 F. or evenhigher. Except for a portion of the downcomer to be described in greaterdetail hereinafter, the downcomer 12 may be of conventional constructionand operation.

As the gaseous discharge from the cupola furnace 10 passes downwardlythrough the downcomer 12, it is saturated with water vapor as it passesthrough an intense water spray and the resulting vapor is condensed, ina manner to be described in greater detail hereinafter, whereby thegaseous discharge is cooled below saturation temperature to l00 F. oreven lower. A portion of the pollutants, generally the larger sizeparticles, is collected, and larger masses of generally smaller sizeparticles are formed. Among the phenomena which take place at the zoneof saturation and condensation are the aggregation of many smaller sizeparticles into larger particle masses and the formation of waterdroplets and aerosols containing small particles. The larger particlemasses and the droplets and aerosols containing particles are of alarger size than the small particles themselves so that the portion ofthe pollutants not captured in the downcomer is in better condition forcollection by the gas-washing equipment located downstream from thedowncomer and to be described in greater detail hereinafter.

Generally, the larger size particles fall freely into a conicalcollector 16 at the bottom of the downcomer 12. In addition, some of theparticle-laden droplets fall into the conical collector 16. Thesepollutants are flushed out of the conical collector 16 through a pipe 18to a tank 20. Tank 20 may be a sedimenting tank or a recirculation tankwhere water is held for reuse in the spray system in the downcomer. Thespray systems receive the required quantities of water by means of apair of pumps 22 and 24 which pump clean water from the tank 20 througha pair of valves 26 and 28.

The reduction in temperature of the gaseous discharge permits passingthe gaseous discharge containing the uncollected pollutants to gaswashing equipment downstream of the downcomer where those pollutants notcaptured by the downcomer are collected. A duct system 30 communicateswith the downcomer 12 at the lower end of the downcomer and extendsupwardly to a crest where it undergoes a reversal in direction andextends downwardly to a wet-type collector 32 of conventionalconstruction and operation. A spray pattern of washing liquid dropletsis developed in the collector 32 in the usual manner, for example bymeans of a rotating cage distributor driven by a motor 34 similar to thedistributor 60 illustrated in FIGS. 4 and 5. The gaseous dischargeintroduced to the collector 32 passes through the spray pattern ofwashing liquid droplets developed therein. Particulate matter isentrapped by the washing liquid droplets and thereby collected. Byhaving preconditioned the gaseous discharge in the downcomer, thecollector 32 is more effective in removing pollutants, particularly theparticles in the submicron size range, from the gas delivered from thedowncomer.

A duct 36 leads form the collector 32 to a moisture eliminator 38 which,in turn, communicates with an exhaust stack 40 through a duct 42. A fan44, located at the base of the stack and driven by a motor 45, draws thegaseous discharge from the cupola furnace 10 through the downcomer 12,the duct system 30, the collector 32, the duct 36, the eliminator 38 andthe duct 42. The moisture eliminator 38 serves to remove washing liquiddroplets which may be carried out of the collector 32 by the draftcreated by the fan 44. The output from the eliminator 38 is drawnthrough the duct 42 and released to the atmosphere through the exhauststack 40.

FIGS. 2 through 6, inclusive, are various views illustrating one type ofequipment which is found highly efficient for developing an intensespray pattern of liquid droplets within the downcomer 12 for saturatingthe gaseous discharge from the cupola furnace l and for condensing theresulting vapor. For the embodiment illustrated, this equipment includesthree spray generator units disposed l20 apart in the downcomer l2 andhoused in shells 50, 52, and 54 in the wall of the downcomer in such amanner as to be out of the flow of the hot gaseous discharge as itpasses through the spray pattern.

FIG. 4, which is a vertical section taken along line 4-4 of FIG. 3, andFIG. 5, which is a horizontal section taken along line -5 of FIG. 4,illustrate the details of the spray generator units. Each of these unitsincludes a stationary pipe 56 to which water is supplied under pressure.The pipe 56 has an opening at its upper end which extends forapproximately 180 around its periphery and is bounded on its lateraledges by side members 560 and 56b. A sloping cap 58 serves to close offthe upper end of the pipe 56. By means of this arrangement, water isejected from the pipe 56. By means of over a limited angle, namely, theangle of the opening in the upper end of the pipe. in other words, thespray pattern, instead of expanding outwardly for the full 360 as in theprior art, extends out only along a sector (creating a spray patternwhich may be thought of as an angular segment of a cylinder).

Surrounding the pipe 56 is a bladed distributor 60. The distributor 60includes a flange 62 to which is secured a plurality of blades 64, mostclearly illustrated in FIG. 5. The opposite edges of the blades 64 aresecured illustrated as secured in a substantially radial arrangement toa ring 66 which is provided to increase the rigidity of the unit.

The flange 62 is coupled to a motor 68 by suitable means. Motor 68causes the distributor 60 to rotate about pipe 56 so that as water isejected from the pipe and impinges upon the blades 64, water dropletsare developed which are thrown into the downcomer.

The three spray generator units function together to develop an intensespray of liquid droplets within the downcomer. In order to develop themost efiective spray and to prevent channeling of the gas through areasdevoid of liquid spray as the gas passes through the downcomer, caremust be exercised in the design of the various components whichcontribute to the development of a uniform spray. Some of the factorswhich have a bearing upon the effectiveness and intensity of the sprayare the shape of the blades 64, the size and angle of the opening in thepipe 56, and the speed of rotation of the distributor 60.

As the water droplets thrown into the downcomer hit the gaseousdischarge, the droplets evaporate thereby cooling the gas by the energyabsorbed by the latent heat in evaporation of the water. The spray is sointense that a level of saturation of the gas is reached. Furthercooling in the heavily water-saturated environment with excess of coolwater droplets within the downcomer beyond the spray generator zonecause condensation of a portion of the resulting vapor on particulatecontaminants which form the seed nucleus similar to the mechanismwherein water vapor of the atmosphere forms mist and rain drops withdust particles in the atmosphere. Where enough minute liquid dropletsencasing particulate contaminants join together or otherwise attractenough liquid, then large enough drops are formed to cause much of thecontaminants of the gas to literally rain out of the gas and catch inthe collector 16. Other particles are removed by the physical washingcaused by the falling liquid drops. Those particles not removed in thedowncomer are preconditioned into droplet form to be more readilyremoved in the conventional air washer (i.e., collector 32). It is alsonoted that the saturation of the gas in the downcomer in many casesresults in some of the contaminating gaseous contaminants being absorbedinto the rapidly formed condensed liquid droplets. This aforementionedadditional cooling may be achieved either by providing additional waterfrom the spray generator units so as to cool the saturated gas or by theintroduction of ambient air. For the embodiment being described, ambientair is introduced into the downcomer 12 through a tangential inlet 74,most clearly illustrated in FIG. 6, to condense the gaseous water vapor.This inlet is located just below the zone at which the gas is saturated.A nozzle-shaped restriction is provided in the downcomer in the vicinityof inlet 74 to restrict the flow of the gas in the downcomer. Thisnozzle-shaped restriction is formed by an open inverted truncated cone70, the sides of which extend from the inside wall of the downcomer 12.The truncated cone 70 creates turbulence in the flow of the gaseousdischarge passing downwardly through the downcomer 12 so as to improvethe mixing of the ambient air which is in troduced into the downcomerthrough the tangential inlet 74 with the saturated gas. As a result,more of the vaporous gas is condensed into droplets giving betterconditioning of the gas for the subsequent gas-washing operation.

lt has been found that use of an afterbumer before the downcomer 12 in acupola furnace system incorporating the present invention gives anunexpectedly significant improvement in the removal of contaminants.Afterburners have been used in the past with cupola fumace systems forthe conventional purpose of burning off dangerous carbon monoxidepresent in the fumes from the furnace and for reducing several otherparticulate contaminants, particularly organic, to harmless gases. Suchsystems incorporating afterbumers have occasionally also includeddowncomers which have simple nozzle sprays giving low-volume,low-velocity, nonuniform, nonsaturating water spray patterns with coarsedroplet sizes presenting very limited liquid surface exposure to the gasflow and also negligible velocity and impingement of the droplets intothe gas flow area. These systems were not noticeably improved bycoupling with afterbumers. The unique improvement found to occur whenafterburners are coupled with a downcomer l2 incorporating the presentinvention appears to result from two reasons; although applicants do notwish to be limited by any theory advanced to explain this or any otheraspect of their invention. It appears that the high temperaturesgenerated by the furnace and the afterbumer physically and chemicallyactivate the surfaces of inorganic particulate contaminants e.g.,desorbing gases from iron oxide) causing them to attract one another andalso adsorb water vapor in the new intense water spray gas cooling andsaturating zone with formation of small droplets so as to combine orcoalesce therewith to fonn relatively larger conglomerations which aremore easily removed from the gaseous discharge. Because of the elevatedtemperatures generated by the afterburner in excess of the heat from thefurnace, which results in a greater temperature difierential in thedowncomer particularly at the spray zone, by the present inventionassure these previously heat surface-activated particles in beingpresent in their activated state so as to be subjected while in thisstate to intimate contact with saturating and cooling water vaporatmosphere resulting in more vapor being adsorbed and condensed out withmore contaminants therefore being removed. In one test, a gaseousdischarge introduced into the downcomer at a temperature of l,000 F. wascooled to a temperature of 1 F.

Various alternative arrangements of the equipment may develop theintense spray in the downcomer, for example, more than three segmentedspray generator units disposed at different angles than may be employed.In addition, the spray generator units may be positioned at differentlevels within the downcomer. Furthermore, more than one set of spraygenerator units may be provided so as to result in multiple saturationand condensation zones.

In certain applications, it may be desirable or even necessary, toprovide another cooling stage in the moisture eliminator. For example,gases having an extremely high proportion of submicron size particlesare difficult to clean. By providing cooling stage in the moistureeliminator, additional washing, entrapment and cooling takes place. Inparticular, larger masses containing smaller size particles also areformed in the eliminator. As the droplets are collected in the moistureeliminator, particulate matter, for example, contained in the dropletsalso is collected. ln addition, because of the conden sation whichresults from this cooling, the moisture content of the gas is reducedand steam plume thereby is reduced.

One preferred arrangement for effecting the desired cooling in themoisture eliminator is by cooling the water supplied to a system ofoverflow troughs. These troughs may be positioned above the moisturecollecting surfaces so that cleaning liquid drains over these surfacesto keep them clean. In order to provide the desired additional coolingin the moisture eliminator, the temperature of the overflow liquid mayrange from 45 F. in the winter to 90 in the summer.

Although the invention has been described in connection with the removalof pollutants from the gaseous discharge of a cupola furnace, it will beapparent that the invention may be employed for cleaning contaminatedgases originating at other sources. In this event, a chamber, opened orclosed to the atmosphere and generally similar to the downcomer 12, isprovided. The contaminated gas is saturated with a selected liquid so asto develop a vapor from this liquid which can be condensed to captureair borne solid particulate matter and aerosols or which will be anabsorbing media for gaseous molecular species. The nature of the liquidused to saturate the contaminated gas is dependent upon the particularoperation in question. If the contaminated gas is not introduced to thischamber at a high temperature, it may be necessary to refrigerate thespray liquid or the cooling air or both in order to condense thevaporous gas. If additional cooling is provided in the moistureeliminator it may be necessary to refrigerate the cooling liquid at thisstage also.

While there have been described what are at present considered to be thepreferred embodiments of this invention it will be obvious to oseskilled in the art that various changes and modifications may be madetherein without departing from the invention and it is, therefore, aimedto cover all such changes and modifications as fall within the truespirit and scope of the invention.

We claim:

1. Apparatus for generating a sector spray pattern comprising rotaryspray generator having a plurality of blades symmetrically arrangedsubstantially radially about its axis of rotation, said blades beingenclosed top and bottom axially and open radially, a liquid supply meanshaving a feed orifice closely adjacent to the inner end of said bladeswith said orifice being an angular opening approximately equal to theangular sector of spray to be emitted, said orifice not having anyangularly overlapping orifices immediately beyond said angular opening.

2. Apparatus as claimed in claim 1 wherein said angular opening subtendsa plurality of blades.

3. Apparatus as claimed in claim 2 wherein said rotary spray generatorfurther comprises a disk support structure, a plurality of curved bladesin radially symmetrical orientation depending from one side of saidsupport structure, each blade being mounted thereon with its concavesurface facing in the same rotational direction, the inner portion ofeach blade being equidistant from the axis of rotation, the innerportion of the concave blade surface making an acute angle with a radiusfrom the axis of rotation through the leading edge of said innerportion. 1

4. Apparatus as claimed in claim 3 further comprising a ring supportstructure fixed to said blades opposite said disk support structurethereby enclosing at least the substantial portion of the blades andforming a central access opening to the inner portions of said blades.

5. Apparatus as claimed in claim 4 wherein the side edges of said bladesare entirely enclosed by said support structures and the latter arecircular in outline with their outer periphery substantially coterminouswith the outer ends of said blades and with the inner periphery of saidring support structure being substantially coterminous with the innerends of said blades.

6. Apparatus as claimed in claim 5 wherein said liquid supply means is apipe capped by a flat plate across the end of said pipe, said pipe has aside opening orifice with lips extending substantially out to the circledefined by the inner ends of said blades.

7. Apparatus as claimed in claim 6 wherein said flat plate slopes backfrom the end of said pipe towards the side opening orifice such that theheight of said orifice positioned withing the rotary spray generatorextends from near said ring support structure to substantially belowsaid disk support structure whereby the flow along said pipe iseffectively turned l to be substantially evenly fed along the height ofsaid blades.

8. Apparatus as claimed in claim 2 further comprising drive means forsaid spray generator, housing pod enclosing said spray generator saidpad having a side opening for accommodating the spray from saidgenerator, said drive means being mounted external to said pod.

2. Apparatus as claimed in claim 1 wherein said angular opening subtendsa plurality of blades.
 3. Apparatus as claimed in claim 2 wherein saidrotary spray generator further comprises a disk support structure, apluRality of curved blades in radially symmetrical orientation dependingfrom one side of said support structure, each blade being mountedthereon with its concave surface facing in the same rotationaldirection, the inner portion of each blade being equidistant from theaxis of rotation, the inner portion of the concave blade surface makingan acute angle with a radius from the axis of rotation through theleading edge of said inner portion.
 4. Apparatus as claimed in claim 3further comprising a ring support structure fixed to said bladesopposite said disk support structure thereby enclosing at least thesubstantial portion of the blades and forming a central access openingto the inner portions of said blades.
 5. Apparatus as claimed in claim 4wherein the side edges of said blades are entirely enclosed by saidsupport structures and the latter are circular in outline with theirouter periphery substantially coterminous with the outer ends of saidblades and with the inner periphery of said ring support structure beingsubstantially coterminous with the inner ends of said blades. 6.Apparatus as claimed in claim 5 wherein said liquid supply means is apipe capped by a flat plate across the end of said pipe, said pipe has aside opening orifice with lips extending substantially out to the circledefined by the inner ends of said blades.
 7. Apparatus as claimed inclaim 6 wherein said flat plate slopes back from the end of said pipetowards the side opening orifice such that the height of said orificepositioned withing the rotary spray generator extends from near saidring support structure to substantially below said disk supportstructure whereby the flow along said pipe is effectively turned 180* tobe substantially evenly fed along the height of said blades. 8.Apparatus as claimed in claim 2 further comprising drive means for saidspray generator, housing pod enclosing said spray generator said padhaving a side opening for accommodating the spray from said generator,said drive means being mounted external to said pod.